This invention relates to unidirectional rotary expansion steam power units of the type having a planetating rotor, and more particularly to an improvement in means for effecting rotation of the rotor in such engines.
In rotary expansion steam engines of the Wankel type, the flow of pressure fluid into the working chambers is controlled by valves external to the engine cavity, the action of which valves is synchronized with the rotor motion through the crankshaft and gear trains or like systems. Such engines are known as variable cutoff or variable displacement engines because the amount of steam admitted, and hence the expansion thereof, may be varied by altering the time during which the inlet valves are open. This necessity for external valves and mechanisms for timing their operation results in an expansion engine of relatively great complexity, bulkiness, and cost. Therefore, expansion engines of the Wankel type have not heretofore been competitive with sliding vane type expansion engines, in spite of the greater capability and efficiency of the Wankel type engines.